Document scanners convert a visible image on media, such as and not by way of limitation, a document, photograph or a transparent media, into an electronic form suitable for copying, storing and processing by a computer. A document scanner may be a stand-alone device or integrated with a copier, a facsimile machine, a digital sender, or a multifunction device. Documents, or media, to be scanned may generally be classified as either transparent or opaque.
For opaque media, light is reflected off an image on the surface of the document onto a photosensitive device/s by a process referred to as a reflective scan. The photosensitive devices convert received light intensity into one or more electric signals. Transparent media are scanned by passing light through, rather than reflecting light off of, the document such as a 35 mm negative, whereupon the light is gathered by an optics system and directed onto an array of photosensitive devices. Transparent media may include either positive or negative images thereon. Document scanning systems operable to scan both transparent and opaque documents are available. Some conventional scanners include a separate light source to backlight the image on the transparent media. The backlight source may be included in a separate transparent media adapter. Alternatively, the backlight source may be integrated within the scanner equipment such as in the cover that overlays the scanner platen. Still other techniques for scanning both reflective and opaque documents include a completely passive adapter used in conjunction with a reflective scanner. Passive adapters do not require an additional light source for backlighting the transparent media. For example, one passive adapter for backlighting a transparent media collects light from the internal lamp of the reflective scanner that passes outside the area of the transparent media and reflects the light through the transparent media where it is gathered by the optic system. Other techniques for combining reflective and transparent media scanning into a single scanner device may be possible.